Absorber for a solar heating panel

ABSTRACT

An absorber for a solar heating panel, designed to contain heat-bearing liquid, and including first and second metal plates fixed to each other in a sealed manner, a matrix of geometrical shapes applied in relief on each of the first and second plates, with the matrices being staggered so as to trace a path for the circulation of heat-bearing liquid in the absorber, and first and second end-pieces placed at the ends of either of the plates so as to provide for circulation of heat-bearing liquid in the absorber, wherein the metal plates are copper plates, and in that non-traversing mechanical connecting means are used to attach the two copper plates together.

TECHNICAL FIELD

In general, this present invention concerns a solar heating panel used for the conversion of light into heat. More particularly, this present invention concerns an absorber for a solar heating panel designed to contain the heat-bearing liquid or fluid of the panel. The invention also concerns a process for the manufacture of such an absorber.

TECHNOLOGICAL BACKGROUND

From prior art, we are aware of many types of solar heating panels that include an absorber containing heat-bearing liquid, such as water, for example, or water mixed with anti-freeze, or air. According to a first category of solar heating panels represented in FIG. 1, these panels 1 include an absorber 2 formed by tubes 3 fitted with fins in which heat-bearing liquid flows in a closed circuit. The tubes are heated in the conventional manner by solar radiation and transmit the heat to a heat-bearing liquid that is flowing inside these tubes. In order to obtain greater efficiency, the absorber is placed in an insulating glazed box, not shown here, in order to achieve a greenhouse effect. A reflector is generally placed under the tubes so as to further increase heat recovery.

Another type of existing flat-plate solar-thermal collectors has an absorber plate to which fluid circulation tubes are attached. The absorber, usually coated with a dark selective surface, for instance a metal plate laid out under the panel of glass, assures the conversion of the sun's radiation into heat, while fluid circulating through the tubes, for instance fine curving metal conduits arranged over the entire length of the panel and containing the heat-bearing liquid, carries the heat away where it can be used or stored. The heated fluid is pumped to a heat exchanger, which is a coil in the storage vessel or an external heat exchanger where it gives off its heat and is then circulated back to the panel to be reheated.

Such solar heating panels nevertheless have a certain number of drawbacks, among which particularly feature the complexity and the mechanical fragility of the absorber as well as a relatively poor efficiency due to the low volume of heat-bearing liquid for a given glazed area of heating panel.

According to a second category of solar heating panels, they include an absorber 4 formed by first and second steel plates welded to each other in a sealed manner, to which is applied a matrix (X, Y) of identical rectangular geometrical shapes 5, 6 in slight relief. The matrices are staggered so as to trace a path for the circulation of heat-bearing liquid in the absorber. Such an absorber 4, although mechanically simpler than those that have tubes, remain mechanically fragile and with inadequate efficiency. In fact, it was observed in the context of this present invention that the use of steel, firstly did not contribute the desired heat efficiency since it is not a good conductor of heat, and secondly rendered difficult or even impossible the chrome-plating of the upper surface of the absorber to allow an increase in its efficiency. Moreover, it was observed that the expansion of heat-bearing liquid contained in the absorber leads to pressures on the plates causing the welds of attachments to fail. Finally, it was also observed that the creation of rectangles in relief firstly proved difficult due to the strength properties of the steel, and secondly generated waste from abrasion of the steel remaining in the absorber and thereafter mixing with the heat-bearing liquid, resulting in clogging of the pumps in the heating panel.

SUMMARY OF THE INVENTION

The aim of this present invention is to overcome the aforementioned drawbacks by supplying an absorber firstly that is effective, meaning one that gives optimised heat efficiency, and secondly that is simple and robust, meaning one that can reliably support the pressure of the heat-bearing liquid that it contains.

To this end, according to a first aspect, this present invention concerns an absorber for a solar heating panel that is designed to contain a heat-bearing liquid, including first and second metal plates fixed to each other in a sealed manner, a matrix of geometrical shapes, applied in relief to each of the first and second plates, with the matrices being staggered so as to trace a path for the circulation of heat-bearing liquid in the absorber, and first and second end-pieces placed at the ends of either of the plates so as to provide for circulation of the heat-bearing liquid in the absorber, and wherein the metal plates are attached together by non-traversing connecting means and wherein the upper face of the top plate, exposed to light radiation, is in copper.

The use of the copper as the metal for the top plate has the considerable advantage of being a good conductor with a heat efficiency that is much better than the metals or alloys used previously. In addition, the copper can be pressed more easily, allowing the creation of geometrical shapes with a larger relief so as to let pass more heat-bearing liquid. Moreover, copper allows the use of a non-traversing connection method that provides not only perfect sealing of the interior of the absorber, with no wastes, but also excellent holding of the plates together, unlike fixing of the plates by conventional welding, with possible separation during expansion of the heat-bearing liquid contained in the absorber. Thus, this present invention is notable in that it succeeds in combining the use of copper for the top plate with good heat efficiency with a fixing system by a non-traversing connection providing excellent holding and perfect sealing.

According to an advantageous variant, these connecting means between the plates are ultrasonic welds. Ultrasonic welding has the great advantage of attaching the two plates together in a sealed manner and without leaving metallic chippings or any other materials between the plates.

According to this advantageous variant, ultrasonic welds are applied on at least one part of the contact portions between the two plates, located between the geometrical shapes and preferably, on each of the contact portions between the two plates, located between the geometrical shapes. Thus fixed, the two metal plates are capable of supporting expansion of the heat-bearing liquid without breaking apart, while not obstructing the circulation of the liquid in the absorber. Advantageously, edges of both plates are connected together by a continuous ultrasonic weld.

According to another variant, the connecting means are rivets attaching the two plates without traversing either.

According to another variant, the connecting means are achieved by clinching the two plates. Clinching is a technique for the mechanical assembly of metal plates. The principle is to connect the two copper plates by pressing or stamping between a punch and a die. This clinching technique has significant advantages since it requires no addition of material, unlike spot welding for example, and it allow the assembly of plates of different thickness.

According to one advantageous variant, the bottom plate is in aluminium, which is more resistant. Such an aluminium plate stiffens the whole absorber while reducing its thickness. Further, it ensures a better support on internal shoulders of the heating panel in which the absorber is incorporated.

According to another advantageous variant, the upper face of the top plate of the absorber, meaning the face exposed to the light radiation, is chrome-plated. As seen previously, the materials used in the prior art allows the application of such chrome-plating to the surface of the absorber only with difficulty and in a costly manner. In the context of this present invention, the use of the copper as the basic material for the top plate of the absorber does allow chrome-plating, that is blackening of the surface of the absorber, further increasing the efficiency of the heating process.

According to one advantageous variant, the geometrical shape is elliptical, and preferably circular. It was shown in the context of this present invention, that a rounded geometrical shape, such as an ellipse or a circle for example, firstly allowed circulation of the heat-bearing liquid in a coil, providing optimised heat efficiency while avoiding retention of heat-bearing liquid through the absorber at any corners in the geometrical shapes of the matrix that can lead to excessive expansion that is undesirable, because of the mechanical strength of the absorber.

According to another advantageous variant, the geometrical shapes are of general bowl form, so as to allow the absorber to hold more heat-bearing liquid, which is heated efficiently due to the better efficiency achieved by this absorber. In addition, it will be noted that this is easily possible due to the metals used to make the plates, meaning copper and aluminium.

According to another advantageous variant, the end-pieces are positioned in a diagonally opposite manner on the lower face of the bottom plate. The end-pieces ensure the circulation through the absorber, with a first end-piece ensuring the entry of heat-bearing liquid into the absorber, while a second end-piece allows the removal of heat-bearing liquid when it has been heated through the absorber. These end-pieces, located advantageously on the lower face, thus have their joints protected from direct exposure to the light radiation, since this could reduce their sealing properties, while keeping the maximum of exposure area on the upper face of the absorber as well as protection for the glass plate used to cover the absorber. Advantageously, the end-pieces are placed on a flat portion of the bottom plate facing a geometrical shape on the top plate, allowing a reduction in the total thickness of the absorber.

According to a second aspect, this present invention concerns a solar heating panel that includes an absorber according to the variant presented above, with the absorber being placed in a frame and covered with a glass plate.

According to a third aspect, this present invention concerns a process for the manufacture of an absorber for a solar heating panel designed to contain heat-bearing liquid, including stages to cut the first and second copper plates, to stamp the first plate by means of a press that includes a matrix of geometrical shapes so as to produce from it a first matrix of corresponding geometrical shapes, to stamp the second plate with an offset by means of the press, so as to produce from it a second matrix of geometrical shapes which is offset in relation to the first matrix of the first plate, to put in place two end-pieces located at the ends of either of the plates, to attach without traversing the two plates together in a sealed manner.

According to an advantageous variant of the process, the two plates are attached together by ultrasonic welding.

According to one advantageous variant of the process, the stamping stages are implemented by means of a press that includes a matrix or die of geometrical elliptical shapes.

According to one advantageous variant of the process, the matrix of geometrical shapes of the press is asymmetrical, and the stamping stages are carried out by introducing the first and second plates respectively at either end of the press. Such an implementation allows creation of the two types of plate, top and bottom, with matrices of staggered geometrical shapes, simply and by means of a single press.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of this present invention will appear more clearly on reading the detailed description that follows of methods of implementation of the invention that are provided by way of non-limiting examples.

FIG. 1 represents a first type of absorber for a solar heating panel according to the prior art;

FIG. 2 represents a second type of absorber for a solar heating panel according to the prior art;

FIG. 3 represents a view from below of an absorber for a solar heating panel according to a preferred method of implementation of this present invention;

FIG. 3 a is an enlargement of an end-piece represented in FIG. 3;

FIGS. 4 a and 4 b represent views in section on axes A-A and B-B, of an absorber for a solar heating panel according to FIG. 3;

FIGS. 5 a to 5 f represent the different stages for the implementation of a process for the manufacture of an absorber according to this present invention;

FIG. 6 represents an example of a solar heating panel that includes an absorber according to one method of implementation of this present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described below only by way of an example, with reference to FIGS. 3 to 6. We will begin with FIG. 3, which represents a view from below of an absorber for a solar heating panel according to a preferred method of implementation of this present invention. The absorber 10 for a solar heating panel is designed to contain heat-bearing liquid. The absorber is created mainly by means of two metal plates 11, 12 which are superimposed and fixed to each other in a sealed manner. Advantageously, the top plate is made of copper and the bottom plate is made of aluminium.

The sealed fixing of the two plates together can be achieved in several ways. A first solution consists in welding edges of the two plates by ultrasonic welding, preferably in one continuous ultrasonic weld which ensures an efficient seal. A second solution is to fold over the edges of one of the two plates and then to slide the other plate into the interstice left between the folded plate and the fold and finally to weld the two plates thus attached. A third solution is to fold over the edges of the two pressed plates at least once into each other, preferably twice, and to trap them between two flat rods in brass or in stainless steel, creating a sandwich, and then to fit a rivet to them at regular intervals so as to clamp the edge thus folded without traversing it, and to render it sealed. Preferably, a 3M adhesive called “sealskin” is added between the plates in order to fully guarantee the sealing effect. This third solution, based on a mechanical clamping system, is more solid than the second solution based on welds, and provides the absorber with an edge that is firmer and more rigid, facilitating handling and fitting in the heating panel. It will also be noted that the brass or steel rods are cut at the corners of the plates so as not to overlap, with the sealing of the corners being achieved by welding.

Each of the metal plates is stamped so as to be covered by a matrix of geometrical shapes 19 applied in relief. The matrix of the top plate and that of the bottom plate are reversed so that the zone of the geometrical shapes in relief is always oriented toward the outside of the absorber. These matrices are also staggered so as to trace a path for the circulation, in a coil, of heat-bearing liquid in the absorber. The elliptical, and preferably circular geometrical shape 19 was chosen as representing the better compromise for circulation of the heat-bearing liquid without a risk of liquid stagnation in some corners due exactly to these geometrical shapes.

It will also be noted that the use of copper and aluminium as the material for these plates allows one to achieve a deeper impression and thus to achieve a larger cupping effect or preferably a bowl shape at the flat bottom of the geometrical shapes 19. This bowl shape has the advantage of increasing the capacity of the absorber and therefore of increasing its potential heat efficiency.

The bottom aluminium plate 11 stiffens the absorber while reducing the overall thickness. In order to optimally capture the light radiation (sunlight for example), the upper face of the top copper plate 12 of the absorber is fully chrome-plated, meaning blackened. Once again, the application of such chrome-plating is rendered easy by the use of copper. Such chrome-plating can be realized, for example, by copper plating a substrate by the deposition of an initial layer of nickel and then a final layer of black chrome. To this end, it will be noted that the upper copper plates used for the manufacture of an absorber are preferably already chrome-plated. It will also be noted that due to the additional cost of these chrome-plated plates, they are chosen with a small thickness.

In order to allow the circulation of heat-bearing liquid between the absorber and the outside, first and second end-pieces 13, 14 are provided, placed at the ends and preferably diagonally and advantageously on the bottom plate 11. Thus end-piece 13 introduces unheated heat-bearing liquid into the absorber 10. The liquid then passes through all of the absorber in a coil through the two staggered matrices, to re-emerge via the other end-piece 14 in the form of heated heat-bearing liquid.

Finally, in FIG. 3, arrows have been shown, indicating the optimises paths in a coil, travelled by the heat-bearing liquid through the absorber 10.

FIG. 3 a is an enlargement of end-piece 13. These end-pieces are preferably screwed rather than welded, so as to facilitate their assembly. A gasket 15 of the O-ring type is arranged between the copper plate and the nut 16 for retention of the end-piece.

Elements 17 represent the non-traversing connecting points between the two top 12 and bottom 11 plates. These connecting points are advantageously ultrasonic welding points. Alternatively, these connecting points may be rivets, preferably cylindrical, advantageously including a cut-out space allowing the compression of the plates without perforation of the latter, with the material being deformed inside this hollow or cut-out. It will again be noted that the interior of the rivet is soaked in adhesive in order to further strengthen the retention of the pressed plates.

According to another variant, the connecting means are obtained by clinching of the two plates 11, 12. Clinching is used to attach the two plates by pressing them between a punch and a die. The copper undergoes local cold plastic deformation, forming a connection point. Cold forming is thus used as an assembly technique.

All of these precautions prove to be important in order to be able to create an absorber that is as flat as possible. In fact, such a mechanical connecting process is used to achieve a very small total thickness at the contacts between the two plates of the absorber of the order of 0.4 cm.

FIG. 4 a shows a first view in section on axis A-A of the absorber 10 of FIG. 3. This first section was taken through the geometrical shapes 19 of the top plate 12 and at the edges of the staggered geometrical shapes 19 on the bottom plate 11. This section clearly shows the coil created by this arrangement, allowing good circulation of the heat-bearing liquid through the absorber.

FIG. 4 b represents a second view in section on axis B-B of the absorber 10 of FIG. 3. This second section was created through the contact zones between the two plates, between the geometrical shapes and where the ultrasonic welds 17 are applied. This section clearly shows the excellent mechanical clamping of the two plates together. To this end, it will be noted that, in the example shown, an ultrasonic weld is applied to each of the contact zones between the two plates, located between the geometrical shapes. However, for economic reasons, it is possible to apply ultrasonic welds only to part of these contact zones between the two plates, located between the geometrical shapes.

FIGS. 5 a to 5 f represent the different stages for the implementation of a process for the manufacture of an absorber according to this present invention.

FIG. 5 a represents a roll of copper used as the raw material for the plates. It is preferable to use a roll for each type of plate, top or bottom, to the extent that for the latter, the copper is preferably chrome-plated in advance and placed in a roll. According to the size of the absorber, and therefore of the desired heating panel, a first stage consists of cutting the first and second copper, respectively aluminium plates from the roll or rolls used.

Then, as shown in FIG. 5 b, a second stage consists of stamping the first plate, by means of a press that includes a matrix or die of elliptical shapes, so as to produce from it a first matrix of corresponding geometrical shapes and then to stamp the second plate with an offset by means of the press so as to produce from it a second matrix of geometrical shapes that are offset in relation to the first matrix of the first plate. It will be noted that advantageously, the matrix of geometrical shapes of the press is asymmetrical and that the stamping stages are thus simply effected by introducing the first and second plates (shown by a broken line) at each end respectively of the press. It will also be noted that the press also includes removable studs, placed diagonally at both of its extremities, used to create two holes at the desired position on the bottom plate, on which the end-pieces will be mounted, with these studs being withdrawn during passage of the chrome-plated copper intended for the top plates of the absorber.

FIG. 5 c shows a stage used to put in place the end-pieces in the perforated positions provided for this purpose, either by screwing or by welding.

FIG. 5 d represents the stage that is used to place the two plates correctly so that the shape matrices are staggered, and to fix the edges of the two plates together in a sealed manner. In this figure the bottom plate is represented below the top plate. This connecting stage in a sealed manner is advantageously carried out by continuous ultrasonic welding. Other alternatives of sealed attachment of the two plates have been described previously. It will also be noted that this connecting stage can be effected after that described below.

FIG. 5 e represents the important stage used to rivet the two plates together without perforating them. The result obtained is represented on the enlargement of FIG. 3b and will therefore not be detailed again here.

Advantageously, sealing tests are performed on the absorber thus created, as represented in FIG. 5 f for example. The opening of one of the two end-pieces is blocked by means of a plug, while the other opening is connected to a tube that puts the absorber under pressure.

It will be noted that the chrome-plated face of the top plate is preferably covered with a protective plastic film from the start of the process, which is removed only at the last moment during the installation of the absorber in the frame of the heating panel. Finally, the absorber created (FIG. 3) by means of this manufacturing process is intended to be incorporated into a solar heating panel.

FIG. 6 represents an example of a solar heating panel that includes an absorber according to any method of implementation of this present invention. The absorber 30 is placed in a frame 31 and covered on the top by a glass plate 32 to create a greenhouse effect between the latter and the top blackened plate of the absorber. The solar heating panel also includes a mechanism to perform the circulation of heat-bearing liquid. Since this mechanism is not directly connected with the principle of this present invention, it has not been shown here.

It will be understood that various modifications and/or improvements that are obvious to those skilled in the art can be made to this present invention as described above, without moving outside the context of the invention as determined by the attached claims. 

1. An absorber for a solar heating panel, designed to contain heat-bearing liquid, and including: first and second metal plates fixed to each other in a sealed manner, a matrix of geometrical shapes applied in relief on each of the first and second plates, with the matrices being staggered so as to trace a path for the circulation of heat-bearing liquid in the absorber, and first and second end-pieces placed at the ends of either of the plates so as to provide for the circulation of heat-bearing liquid in the absorber, wherein both metal plates are attached together by non-traversing connecting means, and wherein the upper face of the top plate, exposed to light radiation is in copper.
 2. The absorber according to claim 1, wherein the connection between both plates is obtained by ultrasonic welding.
 3. The absorber according to claim 2, wherein ultrasonic welds are applied on at least part of the contact zones between the two plates, located between the geometrical shapes.
 4. The absorber according to claim 3, wherein an ultrasonic weld is applied on each of the contact zones between the two plates, located between the geometrical shapes.
 5. The absorber according to claim 4, wherein a continuous ultrasonic weld is applied along all of edges of both plates.
 6. The absorber according to claim 1, wherein the connection between the two plates is achieved by clinching.
 7. The absorber according to claim 1, wherein the connecting means are rivets, clamping the two plates without traversing either.
 8. The absorber according to claim 1, wherein the bottom plate (11) is in Aluminium.
 9. The absorber according to claim 1, wherein the upper face of the top plate, exposed to light radiation, is chrome-plated.
 10. The absorber according to claim 1, wherein the geometrical shape is elliptical.
 11. The absorber according to claim 10, wherein the elliptical geometrical shape is circular.
 12. The absorber according to claim 1, wherein the geometrical shape is a general bowl shape.
 13. The absorber according to claim 1, wherein the end-pieces are positioned in a diagonally opposite manner on the lower face of the bottom plate.
 14. The absorber according to claim 13, wherein the end-pieces are placed on flat portions of the bottom plate facing the geometrical shapes of the top plate.
 15. A solar heating panel including an absorber placed in a frame and covered with a glass plate, wherein the absorber is designed to contain heat-bearing liquid, and includes first and second metal plates fixed to each other in a sealed manner, a matrix of geometrical shapes applied in relief on each of the first and second plates, with the matrices being staggered so as to trace a path for the circulation of heat-bearing liquid in the absorber, and first and second end-pieces placed at the ends of either of the plates so as to provide for the circulation of heat-bearing liquid in the absorber, wherein both metal plates are attached together by non-traversing connecting means, wherein the upper face of the top plate, exposed to light radiation is in copper.
 16. The solar heating panel according to claim 15, wherein the bottom plate is in aluminium and wherein the bottom plate is sustained by internal shoulders of the panel.
 17. A process for the manufacture of an absorber for a solar heating panel designed to contain heat-bearing liquid, including the following stages: to cut the first and second metal plates; to stamp the first plate by means of a press that includes a matrix of elliptical shapes, so as to produce from it a first matrix of corresponding geometrical shapes; to stamp the second plate with an offset by means of the press, so as to produce from it a second matrix of geometrical shapes that are offset in relation to the first matrix of the first plate; to put in place two end-pieces located at the ends of either of the plates; to attach without traversing the two plates together in a sealed manner;
 18. The manufacturing process according to claim 17, wherein both plates are connected together by ultrasonic welding.
 19. The manufacturing process according to claim 18, wherein the stamping stages are implemented by means of a press that includes a matrix or die of geometrical elliptical shapes.
 20. The manufacturing process according to claim 19, wherein the matrix of geometrical shapes of the press is asymmetrical, and in that the stamping stages are effected by introducing the first and second plates respectively into each end of the press. 